Sexual Habits Affect Penis Size in Adulthood

Participants. A total of 282 adult Kazakh males from the Republic of Kazakhstan and who have been visited at the urology units of three university centers in the biggest cities of the Republic of Kazakhstan (Astana, Almaty, and Karaganda) were prospectively included in the study, which took place between January 2020 and January 2021.

Measurements of the penis erect length and girth were by two doctor-urologists according to the method of Veale D et al. (2015).

Statistical analysis. Two-tailed Student's t-test, Pearson correlation and multivariate tests of the MANOVA and MANCOVA (body height as covariate) were used.

Sample size estimation. In a cross-sectional observational study in assessment of erect penis size of Kazakh adult males we supposed that the primary interest lies in assessment of erect penis sizes in the three cities (k=3). The investigators wish to be 95% sure of detecting when the mean erect penis sizes not exceed 1 mm (i.e., 1-β=0.95, and m1=1, m2=0). The standard deviation of erect penis size is likely to be 1.56 mm (i.e. SD=1.56) with a statistical power of 95% and significance level of 2.5% with the Bonferroni correction based on one-sided hypothesis testing. At the 5% Type I error rate (i.e., α=0.05), the sample size of the survey is 196.

Inclusion criteria

• male gender aged from 23 to 35 years
• fill out the questionnaire
• BMI ≤ 29.9 kilogram per meter square
• a male who has at least one healthy native child
• no non-communicable chronic diseases.

Exclusion criteria

• female gender
• BMI ≥ 30.0 kilogram per meter square
• infertility
• erectile dysfunction, previous pelvic surgery, suspected hypogonadism, penile disease, or deformity
• specific treatment with androgens
• alcohol or drug abuse
• history of alcohol consumption ≥ 30 g/day within the past 5 years.